1. Field of the Invention
The invention relates to a navigation device, and in particular, an electronic device configured to operate as a traffic information client, such as a traffic message channel or transport protocol expert group client device, and a method for operating the same.
2. Related Art
Navigation and, in particular, the orientation when driving a vehicle is facilitated by the use of navigation devices, which generally use the global positioning system (GPS) to determine a current position. An indication of the current position together with routing information is provided to a user by means of visible or audio output. Navigation devices usually comprise map data upon which the route to a destination entered by the user or the driver can be calculated. Map information stored on a conventional navigation device is only static, so that when a particular road becomes impassable or blocked (e.g., due to an accident or road works), this is not considered in the route determination.
This drawback was overcome by the introduction of the traffic message channel (TMC). The TMC provides a means for delivering current traffic and travel information (TTI) to the navigation device and the driver. The information on the TMC is generally digitally coded and transmitted by means of a conventional FM radio broadcast. In addition to the TMC, the transport protocol experts group (TPEG) protocol provides a new/additional way of transmitting traffic messages. The TPEG may be used to transport dynamic information about road status to a client device.
TMC or TPEG messages comprise event codes (EC) and a location description, which, in case of TMC will be (and in case of TPEG can be) a location code (LC), and may comprise further information, such as a time limitation (or effect duration), information on the country to which the messages relate, and the like. The event and the location code have to be translated at the client device into information that can be given out to a user, such as into a particular traffic event and a location on the road network. For this purpose, the Traffic Information software (using the TMC and/or TPEG protocol) operating the client device comprises an event code table and a location code table (if TMC locations are the chosen referencing method in case of TPEG).
The event code table and the location code table may be incorporated into conventional devices as either part of the software or stored in the database of the TMC/TPEG client. The tables are stored on the TMC/TPEG client device as binary large objects (BLObs). Such a configuration has several disadvantages. Updating of the event code table and the location code table is difficult and, if the tables are embedded in the software, has to occur together with an update of the TMC/TPEG client software (i.e., the software operating on the client device needs to be updated or re-installed). Similarly, updating the tables is difficult if they are stored as BLObs in a database. The pre-installed TMC tables are generally only appropriate to the market in which the respective TMC/TPEG client devices are sold, and they comprise the TMC event codes and location codes only up to the time of their manufacture. Besides updating, expanding the event and location code tables, for example with a new user language, is difficult.
Due to these limitations, the functionality of the event code and location code tables is restricted. The information comprised in these tables is further generally not suitable for reproducing a correct speech output for a traffic message. Also new types of information can generally not be added to the existing and standardized event code and location code tables.
Storing the tables in the form of binary large objects further requires a relatively large amount of space. When accessing information in the tables, the whole object needs to be loaded into the main memory of the client device, which requires a large amount of main memory and reduces the performance of the device. Similarly, when retrieving data from the tables, access is slow. Present TMC/TPEG client devices accordingly operate rather inefficiently, and are very inflexible regarding the updating or the addition of new information.
In view of the foregoing, a need therefore exists for a traffic information client device that decodes traffic messages with improved versatility and flexibility.